Un-Nooh overcame Liam Highfield in qualifying, and his reward is a second meeting with five-time world champion O'Sullivan, six years after he won their encounter at the German Masters.
The 44-year-old O'Sullivan has given his reaction to facing Un-Nooh in the opening round, and he is certainly not feeling an edge around the match given the good nature of his opponent.
World Championship
Exclusive: O’Sullivan 'hated' seventh world title that dragged him to 'dark places'
"He’s a guy I like playing and one of the few I don’t actually mind losing to as he’s such a nice guy," O'Sullivan told Eurosport after the draw.
Everyone on the circuit would love to see him do well and win tournaments as he’s a very humble and respected by everyone.
Meanwhile, world number one Judd Trump will begin his title defence against Ford, who edged out Stuart Carrington 10-8 in the final round of qualifying.
The tournament starts on Friday and runs until August 16, with all 17 days live on Eurosport and Eurosport Player.

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World Snooker Championship first round draw

  • Judd Trump (1) v Tom Ford
  • Yan Bingtao (16) v Elliot Slessor
  • Stephen Maguire (9) v Martin Gould
  • Kyren Wilson (8) v Anthony Hamilton
  • John Higgins (5) v Matthew Stevens
  • David Gilbert (12) v Kurt Maflin
  • Jack Lisowski (13) v Anthony McGill
  • Mark Allen (4) v Jamie Clarke
  • Mark Williams (3) v Alan McManus
  • Stuart Bingham (14) v Ashley Carty
  • Ding Junhui (11) v Mark King
  • Ronnie O’Sullivan (6) v Thepchaiya Un-Nooh
  • Mark Selby (7) v Jordan Brown
  • Shaun Murphy (10) v Noppon Saengkham
  • Barry Hawkins (15) v Alexander Ursenbacher
  • Neil Robertson (2) v Liang Wenbo
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European Masters Day 1 recap - Selby loses Yuan after Trump wins opener